Pyelonephritis during pregnancy was found to have a higher incidence when the patient's history contained some indication of an earlier renal disease. Pregnancy associated with chronic nephritis has to be interrupted in the first trimester as the particular conditions of pregnancy predispose to pyelonephritis. Provided pregnancy pyelonephritis is diagnosed and treated early enough the incidence of intrauterine fetal death, premature, birth and perinatal fetal loss will not be higher than the average, but developmental retardation has a slightly higher incidence. The degree of renal disturbance not only increase the probability of pyelonephritis but also the damage suffered by the mother and fetus. The prevention of inflammatory renal and appropriate treatment of inflammatory renal diseases and the constant control of the patient is the task of prenatal and nephrological care, so as to avoid early and late complications.